The use of swing flaps fitted to doors to allow the independent exit and entry of pets without having to continually open and close the door, also to prevent any damage to the door as a result of scratching and knocks made by the animals, is a known fact.
An opening is generally made in the door, close to the ground, bordered by a support frame equipped at the top with pins designed to act as hinges for the flap to swing open as a result of the pressure exercised by the animal and close by means of gravity.
It is currently possible to use flaps connected to servomechanisms, for example a linear actuator, which can be controlled by special electronic units that can receive a signal from a transmitter on the collar of the animal wishing to pass through the flap, thus preventing undesired entries and exits.
Current background art also includes solutions that foresee the use of electromagnetic devices consisting of a reed switch and a diode on a circuit which is closed by the entry or exit of the pet wearing a collar fitted with a magnet.
According to other known embodiments, a transponder interacts with an electronic control unit which, by means of actuators, regulates the possibility of opening or closing the flap.
In these cases too, therefore, closure of the circuit enables the movement of one or more actuators which open or close the flap.
According to the background art, the swing flap is equipped with a function selector which ensures a number of possibilities and in particular the opening can be permitted:                for entry into the house only,        for exit from the house only,        for both entry and exit,        for neither entry nor exit.        
This selector usually consists of a knob which is integral with variously shaped elements designed to block the flap directly.
One disadvantage is represented by the fact that, especially if the flap is meant to be used by large animals, only one knob fitted with a blocking device is not sufficient to resist strong pushes in the long term.
Solutions that foresee several knobs with respective blocking devices at the sides of the flap would tend to complicate the selection by the user.